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Sorting out viable induced stem cells from the duds

Researchers may have figured out what makes some induced stem cells duds.

The ethical debate over the use of embryonic stem cells prompted researchers to look for alternatives that might be equally useful. A new paper published in Nature takes a closer look at a less controversial, and less reliable, kind of stem cell called induced pluripotent stem cells (iPSCs). Its authors outline a way to identify which of the iPSCs will be able to develop into any tissue and which ones will be flops by looking for the imprinting of a particular gene cluster.

When gene clusters are imprinted, their expression is altered through chemical modification of DNA or changes in chromosome structure. Embryonic stem cells come with certain genes and gene clusters pre-imprinted as a result of the mother and father's influence. In order for other stem cells to be as useful as embryonic ones, it's likely that they must be imprinted the same way.

IPSCs are the result of activating genes expressed by stem cells in regular cells, causing them to revert to stem cell status. The big problem with iPSCs, though, is that they don't always function in quite the same way that embryonic stem cells do, and often fail to develop into the intended cell type.

When scientists studied a set of mouse-derived iPSCs, they found a correlation between poorly functioning iPSCs and their imprinting: the iPSCs that could not develop as expected had an imprinted Dlk-Dio3 gene cluster. IPSCs that had a normally expressed Dlk-Dio3 cluster, on the other hand, were able to develop fine. With this knowledge, researchers can filter a population of iPSCs for the imprinted cluster and remove the hampered cells from use.

While this doesn't solve any problems with regard to the somewhat high rate of impotent iPSCs, it does does provide a reliable way to identify the duds and remove them from use so that scientists only go forward with working, and ethically unmuddled, stem cells. Still, because iPSCs have a lengthy creation process and a high rate of these duds, we won't be mass-marketing new body parts just yet.

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Casey Johnston
Casey Johnston is the former Culture Editor at Ars Technica, and now does the occasional freelance story. She graduated from Columbia University with a degree in Applied Physics. Twitter@caseyjohnston